GTAW Arc Start issues

[AVGTech]

I could use some help, We have several automated tig weld machines, they apply a tack weld through formed stainless steel sheet, it is 409 ss, no filler material, using 100 Ar shielding gas, we have discussed this will the weld machine manufacturer and they advised attaching a ground lead to the ceramic cups to dischage any built up charges, set gas flow to bewteen 15 to 40 CFH.(searching for a magic flow rate) We still see the problem however it is intermittant.
tungsten is a red 3/32, tip to work piece is about 1/16" to 1/8" still having Arc start problems

 

[stanweld]

Does your power supply provide for "touch-lift" or high frequency starting?

 

[AVGTech]

Yes, it is a maxstar 300, using high freq start

 

[stanweld]

Do you have multiple welding systems working simultaneously and in close proximity? High frequency may adversely affect other units' operating performance. We had this problem and our electrical engineering guru had to devise and add on electrical/electronic systems to adequately filter the "noise" produced during the figh frequency starts.

You may wish to use the "touch-lift" starting method with controlled current ramp up instead.

 

[AVGTech]

yes they all have 2 machines if not 3 about 2 to 3 feet apart
thanks for the info

 

[AeroWeldEng]

To answer your question about argon flow rate, it depends on the type of shielding cup you are using. I recommend using a gas lens to diffuse the gas flow. Then, depending on cup size, your shield gas flow should be 25-30 cfh (for larger cup sizes, you need slightly higher gas flow). Excessive flow rate will de-stabilize your arc, which is likely what your problem was at 100 cfh.